The desirability to convert light, hydrocarbon gases (e.g. natural gas) to liquids (e.g. methanol, gasolines, distillates, etc.) has long been recognized. Probably the most commonly-proposed process for carrying out this type of conversion is one wherein natural gas is first flowed through an Autothermal Reformer, e.g. a partial oxidation reformer, to convert the natural gas to a synthesis gas ("syngas", i.e. a gas comprised of carbon monoxide (CO) and hydrogen (H.sub.2)). The syngas is then fed to a Fischer-Tropsch type of reactor which is loaded with an appropriate catalyst which, in turn, converts the syngas to a desired product (e.g. methanol, gasolines, distillates, etc.) depending on the catalyst and the operating conditions within the reactor. Such processes are well-known in the industry; for examples of Fischer-Tropsch ("F-T") processes of this type, see U.S. Pat. Nos. 1,798,288; 2,500,533; 2,552,308; 4,579,985; and 4,973,453.
While the type of basic process has been known for some time, efforts are continously being made to improve its efficiency in order to make it more commercially attractable. For example, where possible, air instead of oxygen is used as a reactant in the ATR stage since air is obviously cheaper and more readily available than pure oxygen; e.g. see U.S. Pat. Nos. 2,500,533; 2,552,308, et sec. Further, a continuing search is on-going to find the ultimate catalyst for use in the F-T reactor; e.g. see U.S. Pat. Nos. 5 4,522,939; 4,755,536; et sec. Also, improvements in the various elements (e.g. partial oxidation reformer) used in the process are important considerations in attempting to optimize the process (e.g. see U.S. Pat. Nos. 3,549,335; 4,778,826) for commerical use.
Another very important consideration in the commercialization of such a process is maximizing the recovery of otherwise wasted heat and gases from the process for use in the process, itself, or for generating excess energy (i.e. heat and/or mechanical power) which, in turn, can be sold or used in other applications. For example, (a) energy may be generated by reacting off-gas from the process in a fuel cell, see U.S. Pat. No. 4,048,250; (b) dry or tail gas may be used for, generating heat used in the process, see U.S. Pat. No. 4,048,250; (c) heat recovered from a gas turbine, which is used in the process to both compress the process-air and drive an electrical generator, may be used in the ATR, see U.S. Pat. No. 4,315,893; and (d) heat, recovered from the product after it passes through the reformer, may be used to generate a separate stream of superheated steam while the syngas may be expanded through a turbine to recover mechanical energy, see U.S. Pat. No. 4,074,981. While each of these approaches add to the operating efficiency of the overall conversion process, there is still much which can be done in the optimizing the process to make it more commercially acceptable.